• Tejun Heo's avatar
    cgroup: add @flags to css_task_iter_start() and implement CSS_TASK_ITER_PROCS · bc2fb7ed
    Tejun Heo authored
    css_task_iter currently always walks all tasks.  With the scheduled
    cgroup v2 thread support, the iterator would need to handle multiple
    types of iteration.  As a preparation, add @flags to
    css_task_iter_start() and implement CSS_TASK_ITER_PROCS.  If the flag
    is not specified, it walks all tasks as before.  When asserted, the
    iterator only walks the group leaders.
    
    For now, the only user of the flag is cgroup v2 "cgroup.procs" file
    which no longer needs to skip non-leader tasks in cgroup_procs_next().
    Note that cgroup v1 "cgroup.procs" can't use the group leader walk as
    v1 "cgroup.procs" doesn't mean "list all thread group leaders in the
    cgroup" but "list all thread group id's with any threads in the
    cgroup".
    
    While at it, update cgroup_procs_show() to use task_pid_vnr() instead
    of task_tgid_vnr().  As the iteration guarantees that the function
    only sees group leaders, this doesn't change the output and will allow
    sharing the function for thread iteration.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    bc2fb7ed